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Title: Co-existence of Zigbee and Wi-Fi networks : adaptive frequency-temporal co-existence
Authors: Xiang, Tianyu
Keywords: DRNTU::Engineering::Electrical and electronic engineering::Wireless communication systems
Issue Date: 2014
Abstract: Recent large-scale deployments of wireless sensor networks have posed a high demand on network throughput, forcing all the (orthogonal) ZigBee channels to be fully exploited to enhance transmission parallelism. However, the increasing advance of Wireless Sensor Networks are facing threats coming from co-existing WiFi deployments which shares the same 2.4 GHz ISM with ZigBee. The interference from widely deployed WiFi networks has severely jeopardized the usability of these discrete ZigBee channels, while the existing CSMA-based ZigBee MAC is too conservative to utilize each channel temporally. Besides, existing proposals are to pursue as high packet reception ratio as possible on a basis of CSMA plus extra functionalities assessing and handling WiFi interference, but ignoring the demand on high throughput in some application. In this thesis, we propose ART (Adaptive fRequency-Temporal co-existing) as a framework to improve the co-existence status between ZigBee and WiFi in both frequency and temporal manner. Generally speaking, our ART framework consists of two components: FAVOR (Frequency Allocation for Versatile Occupancy of spectRum) [1] and P-CSMA (Probabilistic CSMA). In the first part of this thesis, we will report several experiments on MicaZ Motes. Also, we will explain how those observations and experiences acquired from these experiments motivate our design of an adaptive frequency-temporal co-existing framework, namely, our ART. Specifically, we will introduce the principle of FAVOR [1], which allocates continuous (center) frequencies (thus partially overlapped channels instead of discrete orthogonal channels) to nodes/links in a near-optimal manner, by innovatively converting the problem into a spatial tessellation problem under a united spatial-frequency space. We will also give the mathematical background of this frequency allocation scheme. Besides, we will discuss about the design of our Probabilistic CSMA control scheme. In the second part of this thesis, we present the details of the system model of our ART, which combines our Probabilistic CSMA (P-CSMA) control scheme and FAVOR [1]. We will also propose the details of realization of this Location-Aware Frequency Allocation Scheme. Besides, we will introduce P-CSMA. Based on the knowledge of immediate Packet Reception Ratio (PRR), a CSMA probability can be fine tuned by a transmitter to control the usage of CSMA, achieving a reasonable balance between throughput and PRR in a WiFi-interfering environment. ART employs P-CSMA to opportunistically tune the use of CSMA for leveraging the \temporal white space" of WiFi interference: P-CSMA is a randomized algorithm controlled by a real-time assessment of transmission quality. We will finally introduce the application based on our ART. In the third part of this thesis, we will introduce how to implement ART in MicaZ platforms and gain inspiring insights for practical deployment of it. Specifically, we will present the basic configuration of our ART framework for our experiments, followed by our report of the results we get in different network scenarios. We also briey present a proof of the convergence of the distributed FAVOR [1] algorithm serving as an important component of our ART framework. Finally, we will propose our extensive experiments with different network settings and how they strongly demonstrate the efficacy of ART in enhancing both throughput and transmission quality.
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